Novel coating compositions for high temperature pipes

ABSTRACT

The invention concerns a composition suitable for use as coating for a high temperature oil pipe, comprising at least one thermoplastic polymer selected from the group consisting of polyphenylenes ether or polysulphones, alone or mixed, at least one epoxy resin modified by at least one aromatic polyamine, said resin being formed from at least one polyepoxide containing it its molecule at least two epoxy groups and the aromatic polyamine containing in its molecule at least two primary amino groups, the polyamine, epoxide molar ratio being such that, to each amine group, there corresponds to 1.6 to 2.6 epoxy groups, and at least one filler preferably mineral having an anisometric morphology, preferably selected among the group consisting of silicates such as kaolin, and micaceous iron oxides.

The present invention relates to polymer compositions and their useespecially for coating pipelines, preferably for coating hydrocarbontransport pipes used in offshore oil field exploitation.

In such an application, the principal role of a coating deposited on theoutside of the pipeline onto metal is to protect the metal againstcorrosion induced by sea water, but the coating must also play aprotective role against mechanical damage suffered by the pipe whenplacing it in position or in contact with the sea bottom. Further,current offshore oil developments, in particular the exploitation ofhigh temperature fields where the temperature of the transportedeffluent exceeds 130° C., imposes a raft of ever more demandingrequirements on pipe coating systems. External anti-corrosion coatingsfor transport pipelines must be deposited onto the steel using aconventional process, but this is limited to a temperature of 250° C. toprevent the steel microstructure from being modified. Further,environmental constraints require that non-polluting materials andprocesses be employed. Finally, at the operating temperature in seawater, the coating must have excellent properties of stability, adhesionto the steel and compatibility with cathodic protection systems. Themajority of conventional coatings, however, for example certain powdersbased on epoxy resin sprayed onto the hot pipe, or polyolefins depositedin strips by extrusion, or polyurethanes cast onto the rotatingpipeline, cannot tolerate a continuous operating temperature of morethan 130° C. Such a temperature generally causes deformation of thepolymer and its loss of adhesion to the metal forming part of thecomposition of the pipeline. As a result, in order to satisfy marketdemands, current technological limits in terms of coatings have to bepushed out to provide stability at temperatures of at least 140° C.

United States patent U.S. Pat. No. 6,239,232, for example, describes acomposition acting as a coating for pipelines that not only allows ahigh operating temperature to be employed (up to 180° C. in general) butalso, because a modified resin is introduced, allows the temperature forapplying the composition to the metal pipeline to be reduced to betweenabout 180° C. and 250° C.

During the course of studies carried out by the Applicant, it wasdiscovered that introducing certain filler substances into polymercompositions acting as coatings for metal pipelines at high operatingtemperatures (for example those described in U.S. Pat. No. 6,239,232)not only significantly improved the mechanical strength of said coatingsbut also extended the operating temperature ranges of said coatings, andfinally increased the performance of those coatings after application totheir support. The Applicant has discovered that the stability of thecoating on the pipeline and its behaviour under certain serviceconditions, in particular in sea water, depended largely on the wateruptake of said coating, expressed in the present description as the massof water absorbed (expressed as the percentage by weight) per hundredgrams of coating. Too great a water uptake irreversibly results inplastification of the polymer material by water, encouraging blistering,cracking and finally detachment of the coating. In particular, theApplicant has discovered that a low water uptake provides long-termprotection of the support from corrosion phenomena.

More precisely, the present invention concerns a composition forapplication as a coating for a high temperature oil pipeline, comprisingat least one thermoplastic polymer selected from the group formed byether polyphenylenes and polysulphones, used alone or as a mixture, atleast one epoxy resin modified by at least one aromatic polyamine, saidresin being formed from at least one polyepoxide containing at least 2epoxy groups in its molecule and the aromatic polyamine containing atleast 2 primary amine groups in its molecule, the mole ratio of thepolyamine to the epoxy compound being such that each amine groupcorresponds to 1.6 to 2.6 epoxy groups, and at least one filler,preferably a mineral filler, in the form of particles having ananisometric morphology, preferably selected from the group formed bysilicates in general, such as certain magnesium or aluminium silicates,in particular kaolin, and micaceous iron oxides.

The term “anisotropic morphology” (or non isometric morphology) as usedin the present invention means that said particles have a morphologythat preferably extends in one or more directions in space. As anexample, fillers for use in the present invention can be in the form offibrous, lamellar or, as is preferable, foliate particles.

The mean size of said particles can be in the range 1 to 250 μm,preferably in the range 1 to 100 μm, more preferably in the range 1 to50 μm.

As an example, the greatest dimension of kaolin particles isadvantageously in the range 1 to 30 μm, preferably in the range 3 to 10μm. Similarly, the longest dimension of said micaceous iron oxideparticles is in the range 1 to 60 μm. In general, the longest dimensionof the particles is advantageously more than about 10 μm.

Said particles can have a form factor, defined as the ratio betweentheir largest dimension and their smallest dimension, in the range about5 to 500, limits included, preferably in the range about 5 to 100,limits included, and usually in the range about 10 to 50, limitsincluded, for example in the range about 10 to 20, or in the range 20 to40, limits included. Clearly, the present invention is not limited toform factors as described above and can in particular vary as a functionof the chemical composition of the filler employed. Said values can inthis case be adjusted using any known technique, in particular bycomparative tests carried out using on particles with known dimensions.

The concentration by volume of said particles in the matrix can be inthe range 1% to 50%, preferably in the range 5% to 40%, and usually inthe range 10% to30%.

One or more particle types in accordance with the invention,differentiated by their chemical nature and/or their mean size and/ortheir form factor, can be incorporated into the same composition with aview to improving the properties described above. The mixture of severaltypes of particles having different mean dimensions and/or form factorscan be used to optimize the composition of the invention.

In accordance with the invention, the weight ratio between thethermoplastic polymer and the epoxy resin and the aromatic polyamine orprecursors thereof can advantageously be in the range 70/30 to 30/70,preferably in the range 60/40 to 40/60.

The invention also concerns a coating obtained by applying a compositionin accordance with one of the compositions described above to agenerally metal support. In a variation, the coating is applied to theexternal surface of a pipeline.

Advantageously, the present compositions or coatings can be used in theoilfield exploitation, hydrocarbon transport or refining fields.

The epoxy resin used in the context of the present invention is usuallyselected from the group formed by the following commercial resins: thediglycidyl ether of bis-phenol A or bis-phenol F, bis-phenol formolresin, phenol-novolac resin, cycloaliphatic resins, tri- ortetra-functional resins, resins formed fromtriglycidylether-isocyanurate and/or triglycidylether-cyanurate and/ortriglycidyl-cyanurate and/or triglycidyl-isocyanurate or mixtures of atleast two of said resins. Epoxy resins obtained from epoxy compoundscited in U.S. Pat. No. 4,921,047 can also be used in the context of thepresent invention.

Examples of aromatic polyamines for use in the context of the presentinvention to modify the epoxy resins that can be considered are a firstseries of aromatic amines comprising a single aromatic ring, such as3,5-dimethyl-2,4-diaminotoluene, 3,5-diethyl-2,6-diaminotoluene andmixtures of these two isomers. Usually, a mixture of these two isomers,known as DETDA, is used.

A second series of amines that can be used in the context of the presentinvention that can be considered is the series of amines comprising atleast two aromatic rings, said two aromatic rings generally beingconnected together via a linear or branched divalent hydrocarbon residuecontaining 1 to 18 carbon atoms. Those two aromatic rings are eitherconnected via a divalent alkyl group or are connected to each other viaa linear or branched divalent hydrocarbon residue containing 6 to 18carbon atoms and comprising an aromatic ring.

The aromatic polyamine can also comprise at least one substituentselected from the group formed by fluorine, iodine, bromine andchlorine. It preferably comprises at least two alkyl substituents, eachbeing either side of an amino group.

When the two aromatic rings are connected via a divalent alkyleneresidue, that residue is preferably a non-substituted methylidene group,or a methylidene group substituted with at least one radical selectedfrom alkyl radicals and halogenoalkyl radicals containing 1 to 3 carbonatoms. As an example, said alkylene residue is selected from the groupformed by methylidene, isopropylidene, halogenoisopropylidene andhexafluoroisopropylidene groups. In this case, the amine is preferablyselected from the group formed by:

-   -   4,4′-methylene-bis(2,6-dimethylaniline) or M-DMA;    -   4,4′-methylene-bis(2-isopropyl-6-methylaniline) or M-MIPA;    -   4,4′-methylene-bis(2,6-diethylaniline) or M-DEA;    -   4,4′-methylene-bis(2,6-diisopropylaniline) or M-DIPA; and    -   4,4′-methylene-bis(3-chloro-2,6-diethylaniline) or M-CDEA.

Of those amines, 4,4′-methylene-bis(2,6-diethylaniline) and4,4′-methylene-bis(3-chloro-2,6-diethylaniline) are of particularinterest.

When the amine comprises two aromatic rings which are connected togethervia a substituted or non substituted divalent hydrocarbon residuecontaining 6 to 18 carbon atoms and comprising an aromatic ring, it ispreferably selected from the group formed by:

-   -   4,4′-(phenylene-diisopropyl)-bis(2,6-dimethylaniline);    -   4,4′-(phenylene-diisopropyl)-bis(2,6-diethylaniline);    -   4,4′-(phenylene-diisopropyl)-bis(2,6-dipropylaniline);    -   4,4′-(phenylene-diisopropyl)-bis(2,6-diisopropylaniline);    -   4,4′-(phenylene-diisopropyl)-bis(2,6-dimethyl-3-chloroaniline);    -   4,4′-(phenylene-diisopropyl)-bis(2,6-diethyl-3-chloroaniline);    -   4,4′-(phenylene-diisopropyl)-bis(2,6-dipropyl-3-chloroaniline);    -   4,4′-(phenylene-diisopropyl)-bis(2,6-diisopropyl-3-chloroaniline);    -   3,3-(phenylene-diisopropyl)-bis(2,6-dimethylaniline);    -   3,3-(phenylene-diisopropyl)-bis(2,6-diethylaniline);    -   3,3-(phenylene-diisopropyl)-bis(2,6-dipropylaniline);    -   3,3-(phenylene-diisopropyl)-bis(2,6-dimethyl-3-chloroaniline);    -   3,3-(phenylene-diisopropyl)-bis(2,6-diethyl-3-chloroaniline);    -   3,3-(phenylene-diisopropyl)-bis(2,6-dipropyl-3-chloroaniline);    -   3,3-(phenylene-diisopropyl)-bis(2,6-diisopropylaniline);    -   3,3-(phenylene-diisopropyl)-bis(2,6-diisopropyl-3-chloroaniline);

Preferred aromatic polyamines are selected for their low reactivity andnon-toxic nature.

Within the context of the present invention, it is also possible to addto the composition a highly reactive hardener (i.e. with a reactivitythat is greater than the principal hardener and usually very muchgreater) in small proportions, for example about 1% to 15% by weight andnormally about 1% to 10% by weight with respect to the total compositionweight.

The compositions of the present invention can also contain catalyststhat are active for the reaction between the epoxy resins and thehindered aromatic polyamines. The most frequently used active catalystsare imidazoles, tertiary amines and trifluorinated boron-basedcomplexes. The scope of the invention also encompasses adding otheradditives, usually selected from the group formed by antioxidants,pigments, adhesion promoters, heat and radiation (in particularultraviolet radiation) stabilizers, flame retardants, unmoulding agents,dispersion agents, lubricants, colorants, plasticizers, flame resistantagents, bridging agents, surfactants, surface active agents, reinforcingagents, or mineral or organic reinforcing fibres such as glass, carbonor boron fibres.

The present invention will be better understood and its advantages willbecome clearer from the following examples.

In the examples below, the properties of the compositions of theinvention are described in Examples 2 to 4 and are compared with thoseof a reference compound (Example 1) of the same nature but free of anadditional filler substance, and with those of a composition comprisingsaid reference formulation and a filler substance with a substantiallyisometric morphology (Example 5).

For each composition, measurements of steel adhesion, thermomechanicalbehaviour, stability to seawater and aging behaviour were carried out.

EXAMPLE 1

In this example, a polymer composition comprising a polyphenylene-etherand a modified epoxy resin was prepared.

The modified epoxy resin comprised 8.016 kg of the diglycidyl ether ofbisphenol A (DGEBA) sold by CIBA-GEIGY under the trade name LY556 and3.984 kg of 4,4′-methylene-bis(3-chloro-2,6-diethylaniline) (MCDEA) soldby LONZA.

Prior to being introduced into the extruder, this stoichiometric mixturewas heated to 80° C. with stirring. The reaction progress of thismixture was measured by size exclusion chromatography. The reactivitywas very low: 5 hours at 60° C. resulted in 1% reaction.

The polyphenylene ether or PPE used is sold by GENERAL ELECTRIC underthe trade name Blendex HPP820; its number average molecular mass is12000 g/mol.

The modified epoxy resin was introduced into the extruder using areciprocating pump at a constant rate of 1.30 kg/h. The polyphenyleneether was introduced at a rate of 2.00 kg/h using a weight meteringhopper to obtain a composition containing 40% by weight of modifiedepoxy resin; the percentage of modified epoxy resin was calculated withrespect to the total composition. The processing temperature of themixture was about 180° C.

A homogeneous mixture was obtained from the extruder outlet; theconversion of reactive epoxy functions was less than 10%.

After extrusion, to carry out the adhesion measurements using atensile-shear break test, the reference composition PPE60 was depositedon steel at a temperature of 220° C. then annealed at 220° C. for 2hours.

The composition was then pressed into a mould at a pressure of 5 MPa toform a sheet with thickness 2×10⁻³ m and with a 120×10⁻³ m×120×10⁻³ msurface, and annealed at 220° C. for 2 hours. Subsequently, specimenswere cut from the sheet to determine the thermomechanical properties ofthe composition, along with strips to determine the stability toseawater.

The adhesion properties of the composition in this example weredetermined using the tensile-shear break method (ASTM D1002). Todetermine the adhesion, three steel specimens, which had already beendegreased with a stainless steel brush rotating at high speed, werebonded. The bonding surface was 25.4×10⁻³ m×12.7×10⁻³ m and thethickness of the bond constituted by said composition was 125micrometers. Bonding was accomplished by simple contact at 220° C.,which corresponded to the reduced processing temperature, then thedifferent specimens were annealed for 2 hours at 220° C.

These tensile-shear break adhesion tests were carried out using anapparatus sold by INSTRON (INSTRON-1175) provided with a 100 kN(kilonewton) measuring head, using a cross-head speed of 10⁻³ m/min.

Examples 1.1 to 1.3 in Table 1a relate to three tensile-shear testspecimens for the composition with reference PPE60 and Example 1.4 isthe mean of the preceding results. For each specimen, the maximum loadapplicable prior to rupture was determined. By relating this value tothe bonding surface, the stress at break under tensile-shear could bedetermined. TABLE 1a Examples 1.1 1.2 1.3 1.4 (mean) Maximum load 7.57.6 7.7 7.6 (kilonewton) Stress at break 23.4 23.7 23.8 23.6 (MPa)

It can be seen from this first series of results that the mean stress atbreak in tensile-shear for the reference composition PPE60 was muchhigher than the values required for a coating application.

The thermomechanical properties of the polymer composition of theexample were determined using DMTA (dynamic mechanical thermalanalysis), single clamped. The measurement was carried out on a specimenof thickness 2×10⁻³ m thick, moulded and annealed as described above.The modulus of elasticity values were measured as a function of thetemperature at a frequency of 1 Hz using a Polymer Laboratories DMTAapparatus.

The moduli of elasticity E′ at 25° C., 150° C., 180° C. and 220° C. weremeasured for reference composition PPE60 of the example. These valuesare shown in Table 1b. TABLE 1b Example 1 25° C. 150° C. 180° C. 220° C.Moduli E′, MPa 1260 990 610 70

The moduli of elasticity indicate the rigidity of the materials.According to these results, up to about 180° C., the referencecomposition has sufficient rigidity for application as a coating, butnot beyond that temperature.

A stability to seawater test was also carried out. The annealed moulded2×10⁻³ m thick sheet with the composition of the example was cut intostrips with a surface of 50×10⁻³ m×50×10⁻³ m. Two specimens wereimmersed in synthetic seawater contained in a sealed reactor, heated to160° C. at an absolute pressure of 0.62 MPa. Water absorption tests (orwater takeup tests), expressed as the mass of water absorbed (expressedas the percentage by weight) per hundred grams of coating, were carriedout by determining the variation in the mass of the specimens after 2months and 4 months immersion. The mean results are shown in Table 1c.TABLE 1c Example 1 2 months 4 months Water takeup (% by weight) 1.401.40 Deformation None None

The reference composition specimens did not deform at all after 4 monthsimmersion at 160° C., and had a completely unaltered appearance. Thewater takeup of the reference composition PPE60 was unchanged between 2months and 4 months immersion, indicating that saturation equilibriumhad been achieved.

EXAMPLE 2

Example 2 was in accordance with the invention. In this example, acomposition was prepared based on the reference composition PPE60described in Example 1 and with kaolin, having an anisometricmorphology.

The kaolin used (calcined aluminium silicate) is sold by OMYA, referencenumber Kaolin 2211. It has a specific density of 2.63 g/cm³. The meanparticle size is 1.4 micrometres.

The PPE60 and kaolin were mixed in an extruder heated to 180° C. ThePPE60 granules obtained after a first pass through the extruder usingthe protocol described in Example 1 were introduced via a reciprocatingpump at a constant rate of 2.00 kg/h. The kaolin was introduced using aweight metering hopper at a rate of 1.20 kg/h to obtain a compositioncontaining 20% by volume of kaolin with respect to the totalcomposition.

At the extruder outlet, a homogeneous mixture of polymer was obtained,the conversion of reactive epoxy functions being less than 15%, filledwith kaolin in an amount of 20% by volume.

After extrusion, the composition of Example 2 of the invention wasapplied and annealed using the protocols described in Example 1 tomeasure its steel adhesion, thermomechanical behaviour, stability toseawater and ageing behaviour. The form factor for the majority of saidparticles, measured from scanning electron microscope scans of saidcomposition after said annealing, was in the range 10 to 20.

The adhesion properties of the composition of Example 2 of the inventionwere determined using the ASTM D1002 method using the process describedin Example 1. The results are shown in Table 2a. TABLE 2a Examples 2.12.2 2.3 2.4 (mean) Maximum load 6.1 5.5 6.1 5.8 (kilonewton) Stress atbreak 19 17 19 18 (MPa)

It can be seen from this series of results that the mean stress at breakin tensile-shear of the composition of the invention is very good, andsuitable for use as a coating for oil pipelines, as the relative valuesfor the three specimens were all at least 15 MPa.

The thermomechanical properties of the polymer composition of Example 2of the invention were determined using DMTA analysis, single clampedusing the procedure described in Example 1.

The moduli of elasticity E′ at 25° C., 150° C., 180° C. and 220° C. areshown in Table 2b. TABLE 2b Example 2 25° C. 150° C. 180° C. 220° C.Moduli E′, MPa 2520 1990 1220 200

The moduli of elasticity indicate the rigidity of the materials.According to these results, the composition of Example 2 has sufficientrigidity for application as a coating up to a value of 220° C.

A stability to seawater test was also carried out on the composition ofExample 2 of the invention by means of gravimetric measurements usingthe procedure described in Example 1. Water absorption measurementscarried out by determining the variation in the mass of specimens afterimmersion for 2 to 4 months are shown in Table 2c. TABLE 2c Duration 2months 4 months Water takeup (% by weight) 1.27 1.28 Deformation NoneNone

The specimens of Example 2 of the invention did not deform at all after4 months immersion at 160° C. and had a completely unaltered appearance.The water takeup of the composition of Example 2 of the invention wasstable between 2 months and 4 months immersion, indicating thatsaturation equilibrium had been achieved. The water takeup of thecomposition of Example 2 of the invention was particularly low.

EXAMPLE 3

Example 3 was also in accordance with the invention. In this example, acomposition was prepared based on the reference composition PPE60described in Example 1 and with a micaceous iron oxide having ananisometric morphology.

The micaceous iron oxide used is sold by Kartner, reference number MIOXSF. It has a specific density of 4.80 g/cm³. 15% of the particles have amean dimension of less than 44 micrometres and 30% of particles have amean dimension of 32 micrometres; overall, the particles have a meandimension of less than 74 micrometres.

The PPE60 and micaceous iron oxide were mixed in an extruder heated to180° C. The PPE60 granules obtained after a first pass through theextruder using the protocol described in Example 1 were introduced usinga reciprocating pump at a constant rate of 2 kg/h. The micaceous ironoxide was introduced using a weight metering hopper at a rate of 2.20kg/h to obtain a composition containing 20% by volume of micaceous ironoxide with respect to the total composition.

At the extruder outlet, a homogeneous mixture of polymer was obtained,the conversion of reactive epoxy functions being less than 15%, filledwith micaceous iron oxide in an amount of 20% by volume.

After extrusion, the composition of the example was applied and annealedusing the protocols described in Example 1 to measure its steeladhesion, thermomechanical behaviour, stability to seawater and ageingbehaviour. The form factor for the majority of said particles, measuredfrom scanning electron microscope scans of said composition afterannealing, was in the range 20 to 40.

The adhesion properties of the composition of Example 3 of the inventionwere determined using the ASTM D1002 method using the process describedin Example 1. The results are shown in Table 3a. TABLE 3a Examples 3.13.2 3.3 3.4 (mean) Maximum load 7.1 7.3 6.9 7.1 (kilonewton) Stress atbreak 22 23 21 22 (MPa)

It can be seen from this series of results that the mean stress at breakin tensile-shear of the composition of the invention is very good,suitable for use as a coating for oil pipelines, as the relative valuesfor the three specimens were all at least 20 MPa.

The thermomechanical properties of the polymer composition of Example 3of the invention were determined using DMTA analysis, single clampedusing the procedure described in Example 1.

The moduli of elasticity E′ at 25° C., 150° C., 180° C. and 220° C. areshown in Table 3b. TABLE 3b Example 3 25° C. 150° C. 180° C. 220° C.Moduli E′, MPa 3000 2010 990 220

The moduli of elasticity indicate the rigidity of the materials.According to these results, the composition of Example 3 of theinvention has sufficient rigidity for application as a coating up to avalue of 220° C.

A series of stability to seawater tests were also carried out on thecomposition of Example 3 of the invention by means of gravimetricmeasurements using the procedure described in Example 1. Waterabsorption measurements carried out by determining the variation in themass of specimens after immersion for 2 to 4 months are shown in Table3c. TABLE 3c Duration 2 months 4 months Water takeup (% by weight) 1.141.15 Deformation None None

The specimens of Example 3 of the invention did not deform at all after4 months immersion at 160° C. and had a completely unaltered appearance.The water takeup of the composition of Example 3 was stable between 2months and 4 months immersion, indicating that saturation equilibriumhad been achieved. The water takeup of the composition of Example 3 ofthe invention was particularly low.

EXAMPLE 4

Example 4 was in accordance with a further variation of the invention.In this example, a composition was prepared based on the referencecomposition PPE60 described in Example 1 and a mixture of kaolin andmicaceous iron oxide, described in Examples 2 and 3 respectively.

The PPE60, micaceous iron oxide and kaolin were mixed in an extruderheated to 1 80° C. The PPE60 granules obtained after a first passthrough the extruder using the protocol described in Example 1 wereintroduced using a reciprocating pump at a constant rate of 2.00 kg/h.The micaceous iron oxide and kaolin mixture, pre-mixed in a ratio of15/85 by volume, was introduced using a weight metering hopper at a rateof 1.30 kg/h to obtain a composition containing 20% by volume ofparticles with an anisometric morphology with respect to the totalcomposition.

At the extruder outlet, a homogeneous mixture of polymer was obtained,the conversion of reactive epoxy functions being less than 15%, andfilled with a 15/85 mixture of micaceous iron oxide and kaolin in anamount of 20% by volume.

After extrusion, the composition of Example 4 was applied and annealedusing the protocols described in Example 1 to measure its steeladhesion, thermomechanical behaviour, stability to seawater and ageingbehaviour.

The adhesion properties of the composition of Example 4 of the inventionwere determined using the ASTM D1002 method using the process describedin Example 1. The results are shown in Table 4a. TABLE 4a Examples 4.14.2 4.3 4.4 (mean) Maximum load 6.1 6.4 6.9 6.4 (kilonewton) Stress atbreak 19 20 21 20 (MPa)

It can be seen from this series of results that the mean stress at breakin tensile-shear of the composition of Example 4 of the invention isvery good, suitable for use as a coating for oil pipelines, as therelative values for the three specimens were all at least 20 MPa.

The thermomechanical properties of the composition of Example 4 of theinvention were determined using DMTA analysis, single clamped using theprocedure described in Example 1.

The moduli of elasticity E′ at 25° C., 150° C., 180° C. and 220° C areshown in Table 4b. TABLE 4b Example 4 25° C. 150° C. 180° C. 220° C.Moduli E′, MPa 2700 1910 1130 220

The moduli of elasticity indicate the rigidity of the materials.According to these results, the composition of Example 4 of theinvention has sufficient rigidity for application as a coating up to avalue of 220° C.

A series of stability to seawater tests were also carried out on thecomposition of Example 4 of the invention by means of gravimetricmeasurements using the procedure described in Example 1. Waterabsorption measurements carried out by determining the variation in themass of specimens after immersion for 2 to 4 months are shown in Table4c. TABLE 4c Duration 2 months 4 months Water takeup (% by weight) 1.201.21 Deformation None None

The specimens of Example 4 of the invention did not deform at all after4 months immersion at 160° C. and had a completely unaltered appearance.The water takeup of the composition of Example 4 was stable between 2months and 4 months immersion, indicating that saturation equilibriumhad been achieved. The water takeup of the composition of Example 4 ofthe invention was particularly low.

EXAMPLE 5

Example 5 is not in accordance with the invention. In this example, acomposition was prepared based on the reference composition PPE60described in Example 1 and with particles of zinc phosphate, a fillersubstance with a substantially isometric morphology.

The zinc phosphate used is sold by SNCZ under the trade name PhosphinalPZ04. It has a specific density of 3.30 g/cm³. The zinc phosphate was inthe form of a solid powder with a mean particle size of the order of amicron and with a form factor of close to 1.

The PPE60 and zinc phosphate were mixed in an extruder heated to 180° C.The PPE60 granules obtained after a first pass through the extruderusing the protocol described in Example 1 were introduced using areciprocating pump at a constant rate of 2 kg/h. The zinc phosphate wasintroduced using a weight metering hopper at a rate of 1.50 kg/h toobtain a composition containing 20% by volume of zinc phosphateparticles with a substantially isometric morphology with respect to thetotal composition.

At the extruder outlet, a homogeneous mixture of polymer was obtained,the conversion of reactive epoxy functions being less than 15%, andfilled with zinc phosphate in an amount of 20% by volume.

After extrusion, the composition of Example 5 was applied and annealedusing the protocols described in Example 1 to measure their steeladhesion, thermomechanical behaviour, stability to seawater and ageingbehaviour.

The adhesion properties of the composition of non-inventive Example 5were determined using the ASTM D1002 method using the process describedin Example 1. The results are shown in Table 5 a. TABLE 5a Examples 5.15.2 5.3 5.4 (mean) Maximum load 6.9 7.3 7.1 7.1 (kilonewton) Stress atbreak 21 23 22 22 (MPa)

It can be seen from this series of results that the mean stress at breakin tensile-shear of the composition of Example 5 of the invention isvery good, as the relative values for the three specimens were all atleast 15 MPa.

The thermomechanical properties of the composition of comparativeExample 5 were determined using DMTA analysis, single clamped using theprocedure described in Example 1.

The moduli of elasticity E′ at 25° C., 150° C., 180° C. and 220° C. areshown in Table 5b. TABLE 5b Example 5 25° C. 150° C. 180° C. 220° C.Moduli E′, MPa 2870 1740 1110 310

The moduli of elasticity indicate the rigidity of the materials.According to these results, the composition of comparative Example 5 hassufficient rigidity for application as a coating up to a value of atleast 220° C.

A series of stability to seawater tests were also carried out on thecomposition of comparative Example 5 by means of gravimetricmeasurements using the procedure described in Example 1. Waterabsorption measurements carried out by determining the variation in themass of specimens after immersion for 2 to 4 months are shown in Table5c. TABLE 5c Duration 2 months 4 months Water takeup (% by weight)′112.50 14.20 Deformation marked marked

The specimens of comparative Example 5 exhibited deformation after 2 and4 months immersion at 160° C. and appeared substantially altered(blistering and cracking). The water takeup of the composition ofcomparative Example 5 increased between 2 months and 4 months immersion,indicating that saturation equilibrium had not been achieved. Since thewater takeup of the composition of Example 5 was particularly high andnot stabilized, it can be concluded that said composition is sensitiveto ageing in seawater at 160° C.

Examples 1 to 5 show the possibility of producing compositions frompolyphenylene ether thermoplastic and modified resins, keeping thetemperature for application of said compositions onto steel below 250°C. to produce good adhesion to the steel—in the examples, the stress atbreak in tensile-shear was at least 15 MPa.

However, applying a high temperature coating requires high rigidityunder service conditions; by comparison with reference Example 1,Examples 2 to 4 demonstrate that introducing an anisometric filler intothe polymer composition considerably improves the rigidity of thecoating over the whole temperature range (100% or more gain in modulusbetween 25° C. and 180° C.), and also allows application of the coatingat higher temperatures to be envisaged, between 180° C. and 220° C.(200% or more gain in modulus at 200° C.), which is not possible for thereference composition.

Further, consideration of the stability to seawater appears to be ofvital importance for external coating of a pipeline in a marine medium.By comparison with reference Example 1, Examples 2, 3 and 4 of theinvention clearly show that when the compositions comprise a substancewith an anisometric morphology, the water takeup of the coating isconsiderably reduced compared with the reference composition of Example1 (−10% for Example 2; −20% for Example 3; −14% for Example 4). In thepresent invention, it has been discovered that this reduction in watertakeup conditions the anticorrosion performance of the coating overtime. Thus, a composition comprising a filler with a substantiallyisometric morphology has an increased water takeup compared with that ofthe reference composition of Example 1 (+800%). In the presentinvention, it has been discovered that a large water takeup isassociated with ageing of the coating of the composition, indicated byblistering and cracking.

Overall, these different experiments show that only the compositions ofExamples 2 to 4 of the invention provide a satisfactory response interms of adhesion, thermomechanical behaviour, water takeup and ageingwith a view to applying high temperature coatings to pipelines in amarine medium.

1. A composition comprising at least one thermoplastic polymer selectedfrom the group formed by ether polyphenylenes and polysulphones, usedalone or as a mixture, at least one epoxy resin modified by at least onearomatic polyamine, said resin being formed from at least onepolyepoxide containing at least 2 epoxy groups in its molecule and thearomatic polyamine containing at least 2 primary amine groups in itsmolecule, the mole ratio of the polyamine to the epoxy compound beingsuch that each amine group corresponds to 1.6 to 2.6 epoxy groups, andat least one filler in the form of particles having an anisometricmorphology and with a mean dimension in the range 1 to 250 μm.
 2. Acomposition according to claim 1, in which said filler is selected fromnon isometric silicates.
 3. A composition according to claim 1, in whichsaid filler is a micaceous iron oxide.
 4. A composition according toclaim 1, in which said particles have a form factor, defined as theratio between their largest dimension and their smallest dimension, inthe range about 5 to
 500. 5. A composition according to claim 1, inwhich the concentration by volume of said particles is in the range 1%to 50% with respect to the total volume.